1. Technical Field
The present invention relates to an extruder die design and the spiral-shaped snack food produced by such die. The die uses a unique geometry to induce a consistent spiral shape in a corn-based extrudate. The extrudate is then cut, cooked, and typically seasoned and packaged, thus producing a shelf-stable savory snack food.
2. Description of Related Art
Spiral-shaped pasta in various embodiments has long been known in the food industry. Pasta is typically made from unleavened dough of wheat or buckwheat, flour, and water. Rotini is a particular type of spiral pasta that is made in a helix or corkscrew shape. Rotini is typically made on an industrial scale by extrusion of the wet pasta.
Rotini pasta is produced in a shelf stable dry form which is then later cooked in hot water in order to produce a starch-based food. It would be desirable to produce a ready-to-eat savory snack food made from corn that mimics the rotini shape. Unfortunately, the extrusion process used to produce rotini pasta is incompatible with the rheology of a corn-based dough that can be extruded. However, prior art attempts have been made at producing a rotini-shaped corn snack food.
FIG. 1 shows a prior art process of making a spiral-shaped snack food using corn as the prime ingredient. Cleaned, raw, whole corn kernels are first added to cookers 110 to be cooked in water and lime for typically 20-40 minutes at 180-210° F. This solution is then moved to a soak tank 120 where the corn is further soaked for typically 14 hours and proceeds to a corn washer 130 for the removal of hulls. From the corn washer 130, the corn proceeds to a corn mill 140, which mills the corn. The milled corn is then deposited in an extruder 150. The typical extruder 150 used is a piston extruder. The corn is extruded through a die at the output end of the extruder, and the extrudate is cut into pieces by a cutter 160 before the pieces drop into a fryer 170 for cooking in a hot oil. After cooking, the pieces are sent to a seasoning tumbler 180 for seasoning and, finally, packaged.
In the typical embodiment, the water content of the milled corn prior to extrusion is between 48% and 54% by weight. The extrudate further has a lime content of less than 1% by weight. After frying, the water content of the cooked piece is reduced to between 0.3% and 0.55% water by weight.
The extruder die used in the prior art corn snack process described above is similar to a pasta extrusion die and is shown in FIGS. 2a, 2b, 2c, and 2d. The corn-based product 400 produced by the die described with references to FIGS. 2a, 2b, 2c, and 2d is shown in FIG. 4.
Referring to FIGS. 2a, 2b, 2c, and 2d, a single prior art extrusion die is illustrated. This die is typically co-located with several other identical dies at the output end of the extruder. As noted previously, this die design has been used in the prior art to produce a rotini type pasta. It has also been used in attempts to produce a corn snack product that resembles a corkscrew or rotini type pasta; however, many of the internal surfaces of the die required polishing to make it more suitable for use with a corn based dough. Shown in these figures is a single die in isolation having an input side 220 and an output side 210. On the input side 220 the dough enters the die opening, in which is found a center rod 230 with a hollow core and three directing vanes 240. As the dough proceeds through the die generally parallel to the direction of the rod 230 the dough is progressively constricted until it exits the output side 210 of die through three curved slots 260, each of which has a round tip 250. These three slots 260 are in fluid communication with each other and in fluid communication with the openings defined by the vanes 240. FIGS. 2a and 2c show in phantom some of the relative dimensions of the elements previously described.
Use of the die illustrated in FIGS. 2a, 2b, 2c, and 2d with the prior art process for making a corn-based snack product described above will produce a snack product having a somewhat twisted shape. A typical product 400 produced using this prior art die and prior art method is shown in FIG. 4. The piece 400 shown in FIG. 4 can be seen to be slightly irregular in shape with a fairly small diameter 407 and relatively long pitch 409. It would be desirable if the diameter 407 could be increased and the pitch between flights 409 reduced. Stated differently, a piece 400 having a tighter twist pattern extruded through the unique die would results in a product that is more robust with a crunchier mouth feel. Such product should also have a more consistent spiral or more rotini-type look. It has been observed that using the formulation stated above and this prior art die that the end product is typically neither consistent in the pitch of the spirals nor is the pitch small enough to mimic the rotini-like corkscrew appearance.
Consequently, a need exists for an extrusion die that can provide for a smaller pitch to the spirals and a greater diameter with more consistent looking product. Ideally, this should be accomplished by a change in die design without any need for substantial adjustment to the prior art process for making the corn-based product.